1. Field of the Invention
The present invention relates to a method of forming a fine particle pattern, and a method of producing a device, which includes a step of forming a fine particle pattern by using the method of forming a fine particle pattern.
2. Description of the Related Art
Higher-level integration of semiconductor devices largely contributes to development of computer technology supporting the advanced information society showing a significant progress in recent years. It is estimated that the higher-level integration would be increasingly requested in future. However, there arise a number of problems involved in the higher-level integration, such as narrow channel effects and short channel effects involved in reduction of gate lengths and gate widths, and an increase in gate leak current associated with thinning of gate oxide films.
While investigations have been conducted to solve the above-mentioned problems, researches on a single-electron device eliminating the above-mentioned problems are being conducted.
The single-electron device is a device which is composed of arrayed quantum dots, and controls one electron or few electrons by utilizing a “Coulomb blockade” phenomenon in which tunneling of an electron is suppressed by Coulomb energy.
By using the single-electron device, all of the above-mentioned problems of the current semiconductor devices would be solved, and electric power consumption is expected to be about several ten-thousandths of that required conventionally.
The single-electron device has such a characteristic that a temperature at which the device can operate increases as the size thereof reduces. Therefore, to allow the device to operate at room temperature, an electrostatic capacity thereof has to be about 10 to 18 F.
A dot size and an interval between the dots, which are estimated from the electrostatic capacity, are several nanometers and about 1 nm, respectively.
As a method of forming a pattern of dots of this size, an electron beam lithography or a self-organization of metal fine particles is used (Japanese Patent Application Laid-Open No. 2001-168317).
As well as the higher-level integration of the semiconductor devices, higher recording density of a magnetic recording medium realized by hard disk drives (HDD) largely contributes to the development of the computer technology.
The higher recording density involves a problem of information deletion due to heat fluctuation. To prevent the information deletion, the magnetic recording system is shifting from a longitudinal magnetic recording type to a perpendicular magnetic recording type. In addition, in recent years, there are proposed patterned media.
As a method of producing a recording bit in the patterned media, there is adopted, for example, a method which involves forming a resist pattern corresponding to a desired pattern by the electron-beam lithography, and transferring the resist pattern onto a ferromagnetic layer by dry etching (for example, Japanese Patent Application Laid-Open No. 2005-190624).
In recent years, technologies, which require micro-fabrication in nano-scale order are proposed other than the electron device. For example, there is proposed a chemical sensor to be used for detection and identification of a substance or for an examination of a molecular structure, which utilizes localized plasmon resonance, which occurs near a metal fine particle irradiated with light (Japanese Patent Application Laid-Open No. 2000-356587).
The chemical sensor uses as a sensor chip a device having a structure in which metal fine particles are immobilized in layer on a surface of a dielectric material. The device includes: a unit for applying light to the layer of the metal fine-particles of the sensor chip; and a unit for measuring intensities of wavelengths, which are separated from the light reflected on the layer of the metal fine particles.
It is known that, when the metal fine particles have a uniform particle size and are arranged in a pattern, measurement results can stably be obtained (Japanese Patent Application Laid-Open No. 2003-268592). Formation of the pattern of the metal fine particles or the dot array pattern has conventionally been performed by one of various micro-fabrication techniques or by a combination of at least two of those techniques.
Specifically, examples of the techniques include: lithography and etching using one of ultraviolet light and an electron beam; self-organization arrangement of metal fine particles; arrangement of fine particles by using a probe of a scanning prove microscope such as AFM/STM; and microphase separation of a block copolymer.
Japanese Patent Application Laid-Open No. 2003-168606 discloses a prior art of a method of forming metal fine particles on a surface of a substrate into a pattern by using a combination of the lithography using ultraviolet light or an electron beam and the self-organization arrangement method of metal fine particles.
The formation of the pattern of the metal fine particles described above is performed such that: an organic coating film formed on a substrate is irradiated with an energy beam in a pattern to form a chemically reactive group on the organic coating film; and chemical bonds are generated between the chemically reactive group and an organic coating film on each of the surfaces of fine particles.
Photolithographic techniques using reduced projection exposure of ArF, KrF, or the like to ultraviolet light are used in production of the semiconductor devices. However, the photolithographic techniques have limits of resolution due to the diffraction limit of light, so it is difficult to form a dot pattern having dots in a high density of several tens nanometers.
In addition, the lithography using an electron beam is excellent in resolution, but throughput thereof is small, so the lithography using an electron beam is unsuitable for a large-scale production unit. Further, there is a problem in that an exposure apparatus therefor is expensive.
A resist pattern formed by lithography is transferred onto a metal layer by dry etching using reactive plasma, resulting in problems in transfer accuracy due to re-deposition of an etching product on a substrate to be treated or an etching mask, and occurrence of side etching.
In addition, a multilayer resist method or the like is used for retaining an aspect ratio sufficient for the etching of a metal. In this case, however, there are problems of complication of steps of the method and an increase in cost.
The self-organization method enables formation of a fine pattern to be kept for a short period of time, but has many defects, so there arises problems such as a long-term order in few-inch scale required in a magnetic recording medium or the like, and the reproducibility of the pattern. Further, there are such problems that a desired pattern cannot be formed, and the like.
Japanese Patent Application Laid-Open No. 2003-168606 described above represents results of implementation in which: a chlorosilane compound having an unsaturated alkyl group is formed into a monomolecular film on a glass substrate; the monomolecular film is irradiated with X ray into a pattern so that unsaturated bonds in an irradiated area are excited, to thereby allow the unsaturated group to bind to a monomolecular film on each of surfaces of fine particles. However, the technique disclosed in Japanese Patent Application Laid-Open No. 2003-168606 has such a problem that the fine particles do not sufficiently adhere onto the area irradiated with an energy beam, resulting in many defects. This is because the excited state of the groups, which are bound to each other via the unsaturated bonds is unstable so that the excited state easily returns to a ground state, thereby the groups are deactivated.
As described above, the conventional micro-fabrication techniques have many problems, so it is problematic to apply the conventional techniques to the production of various devices, which require high density dot patterns, which have been newly proposed in recent years. Specific examples of the devices include a single-electron device, a magnetic recording medium, a chemical sensor, a quantum dot laser device, and a photonic crystal optical device.